Boost Leak?

[Dwesson]

I have a 2017 audi b9 s4 with about 31k miles, its currently tuned to a stage 2 with IE.

Mods:
-IE carbon intake
-IE turbo inlet
-IE stage 2
-Wagner Intercooler with chargepipe
-IE high-flow DP

So here is the deal, I got the IC and DP installed back in april, did some logs and car felt great, no complaints. Back in June 30th I got the car detailed, and the detailer cleaned the engine bay (my mistake, first and last time I'm ever doing that), that same night car threw an intermittent "drivetrain error" with no codes, it eventually resolved itself after sitting in the sun for a day. The thing is I felt the car not pulling as hard as before, and maybe an increase in turbo lag/spool time. Did some quarter mile runs and it was .2-.4 seconds slower, so I did some logs form launch and from 4th gear, and noticed turbo is building up boost normally at lower RPM, but at higher RPM it's not reaching the target boost, and the wastegate is duty is high.

I was wondering if you guys think this could be related to an electrical issue, or maybe a mechanical issue as in a loose hose. The logs started showing signs of what I interpret could be boost leak the same day I got the car detailed.

I've checked the hose connections to IC and nothing seems off (getting a leak test on Tuesday), I've changed the diverter valve and nothing changed, I also don't hear any unusual noises or hissing.

Any ideas, comments or recommendations are appreciated.

Here are the datalogs:
4th gear: https://datazap.me/u/johnsmith447/lo...&data=3-5-7-14
launch: https://datazap.me/u/johnsmith447/lo...g=0&data=3-5-7
old logs for comparison (stage 2 but pre car wash): https://datazap.me/u/johnsmith447/lo...g=0&data=2-3-5

[S4James]

dealing with something similar myself, check this thread. Looks like this issue is going to be very common. https://www.audizine.com/forum/showt...too-high/page5

[Dwesson]

Interesting thread, although I haven't had any coolant leaks or high temps, will take a look at it though

[Dwesson]

Update, got a shop to do a smoke test and they found nothing, still baffled at what it could be

[S4James]

your wastegate duty cycle looks maxed out where you start diverging from requested/actual boost. You might be dealing with a failing n75 valve. (06M906609A).... Do what I did and measure vacuum at the valve, both on the wastegate and vacuum source in WOT (4rth gear would be fine)..

You should see lots of vacuum on the source side. Then it varies on the wastegate side.. 100% duty cycle one would think you should be seeing close to what the source vacuum is pulling, in my case 28 inches (around 14lbs)... But in my case on the wastegate side, only 5psi or so. Which is not enough. At least I hope this is whats going on. Ill find out tommorow.

[A4 Centaur]

^ Yea, if you haven't checked your N75 that is the closest part to the actual physical gate. Then you could at least check to see if the waste gate is opening. But if you can put a bore scope down the Lambda sensor hole in front of the Cat and see what is happening there.

[Dwesson]

That would make a lot of sense, maybe the n75 got soaked or corroded with the engine bay wash, and the waste gate is stuck at an open or half open position even if the logs are reading a high waste gate duty cycle? Explaining why its not reaching the target boost with no apparent boost leak. Btw the n75 valve part number u attached is for the 4.0 tfsi engine, do you by any chance have the aprt number for the ea839 engine? I cant find it for the life of me in ECS or FCP euro, thanks!

[S4James]

That would make a lot of sense, maybe the n75 got soaked or corroded with the engine bay wash, and the waste gate is stuck at an open or half open position even if the logs are reading a high waste gate duty cycle? Explaining why its not reaching the target boost with no apparent boost leak. Btw the n75 valve part number u attached is for the 4.0 tfsi engine, do you by any chance have the aprt number for the ea839 engine? I cant find it for the life of me in ECS or FCP euro, thanks!

Thats right from audi based on my vin. It should be correct, ill have it in my hands tommorow. This website shows an application for our cars https://www.oemvwshop.com/06m906609a...rter-p2531975/

[Dwesson]

Thats right from audi based on my vin. It should be correct, ill have it in my hands tommorow. This website shows an application for our cars https://www.oemvwshop.com/06m906609a...rter-p2531975/

Awesome, let me know if it works!

[S4James]

Awesome, let me know if it works!

It worked! No signs of coolant ingress, just plain old broken.

Expensive up here in Canada. almost 300$. But yeah, nobrainer.

[Dwesson]

Welp I ordered a new n75 valve and no go, still low boost :/ back to square 1.

Got a p0236 code earlier on a long drive

[S4James]

you need to measure vacuum and see if you have the dreaded issue with the coolant.